The double perovskite Sr2FeMnO6 has been synthesized by the solid-state reaction method. X-ray diffraction and subsequent Rietveld refinement confirm that Sr2FeMnO6 has the double-perovskite structure with a cubic cell (a=7.726 Å) and space group Fm3m (No. 225) . The appearance of the superlattice reflection (111) indicates that Fe and Mn atoms alternatively occupy the center of oxygen octahedron in an ordered way. Based on magnetization hysteresis curve and ESR measurements, a ferrimagnetic to paramagnetic phase transition for the double perovskite Sr2FeMnO6 was observed, and the Neel temperature was determined to be TN ~475K. In paramagnetic phase above TN, the value of gyromagnetic factor was determined to be very close to 2.